Definition Of Remission Response Criteria

"measurable," to ensure that a decrease in the M protein meeting requirements for response would be of sufficient magnitude to not be considered a laboratory variation. A "measurable" serum M protein is typically defined as >1 g/dL and a "measurable" urine M spike is defined as >200 mg/24 h. Responses cannot be reliably ascertained using M-protein measurements if the baseline values are below the "measurable" threshold.

Standard definition of response and progression

By definition, the criteria require that M-protein reductions be confirmed by consecutive determinations. Responding patients should also have no evidence of progressive disease.

Bone marrow biopsies are not required to confirm PR or MR, but are required for the definition of CR and to evaluate response in patients with nonsecretory myeloma. Skeletal radiographs are not required to confirm response, but should not show evidence of progression if performed. A summary of the criteria listed below is provided in Table 86.1.

Complete response Patients who have complete disappearance of M protein (negative immunofixation on the serum and urine) and 5% or fewer bone marrow plasmacytosis are considered to have achieved a CR. In addition, any soft-tissue plasmacytomas should disappear, and there should be no known increase in the size or number of lytic bone lesions. Patients meeting criteria for CR who have no clonal cells in the bone marrow and have a normal free light chain ratio are categorized as "stringent CR."

Very good partial response The VGPR category is a useful measure of response that has gained clinical signifi cance, as patients who achieve at least a VGPR with the first autologous stem cell transplant do not benefit from a second (tandem) transplant. For practical purposes, it distinguishes patients who have had near disappearance in their M spike but are still immunofixation positive from those who merely have a 50% reduction in their serum M spike. To be considered VGPR, patients must meet all of the following criteria:

■ greater than or equal to 90% reduction of M protein from serum (also includes achievement of a detectable but not quantifiable monoclonal protein by SPEP or by immunofixation only);

■ urine M spike to be <100 mg/24 h (also includes achievement of a detectable but not quantifiable monoclonal protein by urine protein electrophore-sis or by immunofixation only);

■ no increase in size or number of lytic bone lesions.

Partial response To be considered a PR, patients should have a >50% reduction in the level of the serum monoclonal protein and a reduction in 24-h urinary light-chain excretion either by >90% or to <200 mg/24 h. If present at baseline, there should also be a >50% reduction in the size of any soft-tissue plasmacytomas (by radiography or clinical examination), and there should be no increase in the number or size of lytic bone lesions. (Development of a compression fracture does not exclude response.) FLC criteria are used in patients without measurable disease.

In patients with nonsecretory myeloma, a >50% reduction in plasma cells in a bone marrow aspirate and on trephine biopsy must be documented in place of the M-protein and FLC requirements provided baseline bone marrow plasma cell percentage is 30% or

Table 86.1 Response criteria for myeloma

Response category

Monoclonal protein/plasmacytoma

Bone marrow

Complete response (CR)

■ Negative immunofixation on the serum and urine and

■ Disappearance of any soft-tissue plasmacytomas

<5% plasma cells

Very good partial responseb

■ >90% reduction of serum M protein and

■ Serum and urine M protein detectable on immunofixation but not on electrophoresis, or

■ Disappearance of any soft-tissue plasmacytomas

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